Re: Refuse following the vfork parent if not letting the child run.

[Pedro Alves <pedro@codesourcery.com>]

On Monday 08 June 2009 15:40:23, Pedro Alves wrote:

> > Is this actually a fork-following error, and we've stopped execution?
> 
> I guess you could call it an error.  We can't satisfy the users request,
> so we kind of stopped execution --- in reality, we're refusing to
> continue execution, as the inferior is stopped already.

How about?

 (gdb) n
 error resuming execution: can not resume the parent of a vfork in the
 foreground if not letting the child run until it execs or exits, as
 it would lock the terminal and hang the debug session.
 0x00007ffff789aee4 in vfork () from /lib/libc.so.6
 (gdb) 

-- 
Pedro Alves

2009-06-08  Pedro Alves  <pedro@codesourcery.com>

	* linux-nat.c (linux_child_follow_fork): Refuse to follow a vfork
	parent in the foreground if not letting the child run.

---
 gdb/linux-nat.c |   15 +++++++++++++++
 1 file changed, 15 insertions(+)

Index: src/gdb/linux-nat.c
===================================================================
--- src.orig/gdb/linux-nat.c	2009-06-08 13:22:47.000000000 +0100
+++ src/gdb/linux-nat.c	2009-06-08 16:01:40.000000000 +0100
@@ -596,6 +596,21 @@ linux_child_follow_fork (struct target_o
   if (!detach_fork)
     linux_enable_event_reporting (pid_to_ptid (child_pid));
 
+  if (has_vforked
+      && (!target_is_async_p () || sync_execution)
+      && !(follow_child || detach_fork || sched_multi))
+    {
+      /* The parent stays blocked inside the vfork syscall until the
+	 child execs or exits.  If we don't let the child run, then
+	 the parent stays blocked.  If we're telling the parent to run
+	 in the foreground, the user will not be able to ctrl-c to get
+	 back the terminal, effectively hanging the debug session.  */
+      fprintf_filtered (gdb_stderr, _("\
+error resuming execution: can not resume the parent of a vfork in the foreground if not letting \
+the child run until it execs or exits, as it would lock the terminal and hang the debug session.\n"));
+      return 1;
+    }
+
   if (! follow_child)
     {
       /* We're already attached to the parent, by default. */